1. Field of the Invention
Some preferred embodiments of the present invention relate to a semiconductor device, and more specifically to a semiconductor device equipped with a fuse for changing circuit wiring in the semiconductor by blowing the fuse, and also relate to a method of monitoring blowing of a fuse in a semiconductor device.
2. Description of the Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
In recently developing semiconductor devices, for the purpose of enhancing the versatility, it has become popular to change the semiconductor status settings not by changing the mask pattern of the semiconductor device but by blowing fuses mounted in an inner side of the semiconductor to change the wiring connection to thereby, for example, disconnect defective devices and connect redundancy circuits.
In order to change the wiring connection by blowing a fuse to disconnect a part of wiring in a semiconductor device, fusing circuits, such as, e.g., fuse patterns, are formed in the semiconductor device in addition to the electric circuit patterns. An electric stress is applied to both ends of the fusing circuit to blow the fuse element to thereby electrically disconnect the wiring to change the wiring connection (see, e.g., Japanese Unexamined Laid-open Patent Application Publication No. 2007-5424).
FIG. 6(a) shows a schematic view showing an example of a conventional fuse for a semiconductor device. As shown in this figure, the fuse F includes a linear conductive portion 3 and a pair of pads 1 and 2 electrically connected to both ends of the conductive portion 3. The conductive portion 3 arranged between the pads 1 and 2 has a thinner width so that the conductive portion 3 can produce heat by locally increased current density to be blown when a relatively small amount of current flows therethrough. The fuse F shown in FIG. 6(a) is in a state in which the fuse is not blown. When the conductive portion 3 of the fuse F is blown, as shown in FIGS. 6(b) and 6(c), a clearance “C” will be formed at the longitudinal intermediate portion of the conductive portion 3. The clearance “C” is defined by and between the left side remaining portion 3a of the conductive portion 3 and the right side remaining portion 3b of the conductive portion 3. FIG. 6(c) shows a blown state of the fuse in which the sufficiently large clearance “C” is formed. In some cases, however, as shown in FIG. 6(b), there is a possibility that the fuse blows such that the clearance “C” is very small due to variations of applied stresses.
When confirming the fuse-blowing in a semiconductor device with an IC tester, although such an IC tester measures electrically to confirm whether the fuse is blown, the tester cannot measure the clearance “C” (i.e., distance) of the blown-off portion of the fuse F. Accordingly, if there is a clearance “C,” the IC tester indicates that the fuse is blown regardless of the size of the clearance “C.” However, when the clearance “C” between the remaining portions of the fuse F is insufficiently small, the remaining portions of the fuse may sometimes reconnect due to, e.g., temperature stress or force stress. This deteriorates the reliability of the semiconductor.
Especially, in a semiconductor device for use in automobiles, it should be considered to be used under severe conditions, such as, e.g., under extremely high temperatures during high temperature seasons in summer. Thus, such a semiconductor is required to possess high reliability. However, conventional semiconductors equipped with such fuses are not reliable in terms of blowing the fuses.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. For example, certain features of the preferred embodiments of the invention may be capable of overcoming certain disadvantages and/or providing certain advantages, such as, e.g., disadvantages and/or advantages discussed herein, while retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.